Conventionally, a technology providing mobility of an entire network including a movable terminal and a router has been studied in IETF NEMO-WG (“Network Mobility (NEMO) Basic Support Protocol” written by Vijay Devarapalli et al.).
NEMO is technology which enables data accessing to a network including movable terminals and a router (hereinafter, referred to as “moving network”), by a mobile router and a home agent which manages the location of the mobile router. The mobile router is a device which connects a moving network and a global network such as Internet.
Technology of selecting an appropriate mobile router, depending on a type of data and a security condition etc., by including a plurality of mobile routers in one moving network, in the above moving network system (e.g., Japanese Patent Unexamined Publication No. 2003-283546) has been disclosed. In addition, technology for securing robustness by switching the mobile router used when there is load sharing by a plurality of mobile routers, or a failure or connectivity problem with a mobile router is known.
In this Japanese Patent Unexamined Publication No. 2003-283546, each mobile router decides whether to give permission for communication between a terminal working under itself and a global network, on the basis of a preset condition. In the case where the mobile router does not permit the communication, communication passing through an appropriate mobile router is realized by instructing the terminal to use another mobile router.
Hereinafter, a communication method between a terminal on a moving network in which a plurality of mobile routers exist, and a terminal on a global network will be explained by use of FIGS. 1 and 36.
The following explanation assumes use of IPv6, but it is also possible to configure a moving network system by use of IPv4.
FIG. 1 is a view which represents a configuration of a moving network system.
In FIG. 1, moving network 2, which includes mobile routers (MR) 4, 5, terminal 7 and local network 9, is connected to a global network 1 such as Internet through access routers (AR) 3. In addition, home agent (HA) 6 which manages locations of mobile routers 4, 5 and a network identifier of moving network 2, and terminal 8 are connected to global network 1.
Mobile routers 4, 5 acquire Care of Address (CoA) by use of a network prefix which is owned by a connection destination access router (AR). Mobile routers 4, 5 register Mobile Network Prefix (MNP), which is the network identifier set for itself, and Home Address (HoA) which is the unique address in the home network, in home agent 6, by means of a Binding Update packet.
Mobile router 4 or 5 publicizes MNP in a moving network. In addition, terminal 7 in the moving network prepares a terminal address for itself by use of publicized MNP.
Home agent 6 refers to the MNP which is included in the address of terminal 7 when a packet addressed to terminal 7 arrives, and obtains CoA of mobile router 4 or 5 in which the relevant MNP has been registered. Home agent 6 encapsulates the packet addressed to the address of terminal 7, and sets the CoA of mobile router 4 or 5 which in the address of that encapsulated packet, and sets up the address of home agent 6 in the address of the transmission source. Home agent 6 transmits the encapsulated packet.
Mobile router 4 or 5, which receives this encapsulated packet, takes out the packet addressed to the address of terminal 7 out of the capsule, and relays it to terminal 7 in moving network 2.
In addition, a packet is transmitted from terminal 7 to terminal 8 outside moving network 2. At this time, mobile router 4 or mobile router 5 intercepts and encapsulates this packet. Mobile router 4 or mobile router 5 sets the destination to be the address of home agent 6, and sets the transmission source to be the CoA of mobile router 4 or mobile router 5. Mobile router 4 or mobile router 5 transmits the encapsulated packet.
Home agent 6, which receives this encapsulated packet, takes out the packet addressed to terminal 8, from the capsule, and transmits it to terminal 8.
In this manner, mobile router 4 and mobile router 5 are connected to identical local network 9 and configure moving network 2 with the same MNP. In such case, terminal 7 prepares a terminal address for itself on the basis of this MNP, and thereby, both mobile routers 4, 5 can carry out a relay of communication between terminals 7 and 8, and therefore, it becomes possible to secure redundancy and realize load sharing.
FIG. 36 is a view which represents sequence at the time that mobile routers (MR) 4, 5 are registered in home agent (HA) 6.
Firstly, in mobile routers 4 and 5, the identical MNP1 is set to be the network prefix, in order to configure a single moving network 2.
Next, when mobile router (MR) 4 is connected to AR 3, mobile router 4 acquires the Care of Address CoA_MR4, and thereafter, it transmits a location registration request including MNP1 to home agent 6 (step S1001).
Home agent 6 registers mobile router (MR) 4 as the forwarding destination of MNP1 (step S1002), and thereafter, it returns a register confirmation response showing that location registration was successful to mobile router (MR) 4 (step S1003).
When mobile router 5 is connected to AR 3, location registration processing is carried out in the same manner (steps S1004 and S1006), and the forwarding destinations of MNP1 become mobile router 4 and mobile router 5 (step S1005).
Thereafter, in the case where mobile router 5 breaks away from moving network 2 (S1007), home agent 6 permits location registration for mobile router 5 in response to a location registration request from mobile router 5 (step S1008), and returns a response of registration approval (step S1009).
However, it is also conceivable that mobile router 5 acquires MNP1 by any means, but in actuality, it is not connected to moving network 2 to which mobile router 4 has been connected. In this case, there is a case where home agent 6 considers mobile router 5 as the forwarding destination of MNP1, even though mobile router 5 is not connected to moving network 2 in actuality, and transmits data addressed to terminal 7 to mobile router 5. In addition, in the case where mobile router 5 has broken away from moving network 2, it is not possible to know this unless home agent 6 receives a notification of breakaway from mobile router 5. On this account, home agent 6 judges that mobile router 5 is also a forwarding destination of MNP1, and transmits data addressed to terminal 7 to mobile router 5. In consequence, prior art had such a problem that there are cases where data does not reach terminal 7.
Furthermore, even in the case where mobile router 5 is connected to a different AR after it breaks away from moving network 2, mobile router 5 is registered as a router of MNP1. At this time, data addressed to terminal 7 is transmitted to mobile router 5 erroneously, and does not reach terminal 7. There is also the problem that, if an evil-minded user steals mobile router 5 and utilizes this, data addressed to terminal 7 is tapped at a place removed from moving network 2.